The generation of noise in heaters provided with a fan for supplying combustion air to the combustion chamber of the heater is decisively determined by the flow noise caused by the combustion air flow in the fan. In particular with small heaters, as used for example as engine-independent additional heating means in motor vehicles, this generation of noise turns out to be inconvenient because the additional heating means is located in the vicinity of the vehicle passengers due to the as a rule restricted vehicle dimensions.